cliff/cliff/formatters/table.py

#  Licensed under the Apache License, Version 2.0 (the "License"); you may
#  not use this file except in compliance with the License. You may obtain
#  a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#  Unless required by applicable law or agreed to in writing, software
#  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#  License for the specific language governing permissions and limitations
#  under the License.

"""Output formatters using prettytable.
"""

import prettytable
import os

from cliff import utils
from . import base
from cliff import columns


def _format_row(row):
    new_row = []
    for r in row:
        if isinstance(r, columns.FormattableColumn):
            r = r.human_readable()
        if isinstance(r, str):
            r = r.replace('\r\n', '\n').replace('\r', ' ')
        new_row.append(r)
    return new_row


class TableFormatter(base.ListFormatter, base.SingleFormatter):

    ALIGNMENTS = {
        int: 'r',
        str: 'l',
        float: 'r',
    }
    try:
        ALIGNMENTS[unicode] = 'l'
    except NameError:
        pass

    def add_argument_group(self, parser):
        group = parser.add_argument_group('table formatter')
        group.add_argument(
            '--max-width',
            metavar='<integer>',
            default=int(os.environ.get('CLIFF_MAX_TERM_WIDTH', 0)),
            type=int,
            help=('Maximum display width, <1 to disable. You can also '
                  'use the CLIFF_MAX_TERM_WIDTH environment variable, '
                  'but the parameter takes precedence.'),
        )
        group.add_argument(
            '--fit-width',
            action='store_true',
            default=bool(int(os.environ.get('CLIFF_FIT_WIDTH', 0))),
            help=('Fit the table to the display width. '
                  'Implied if --max-width greater than 0. '
                  'Set the environment variable CLIFF_FIT_WIDTH=1 '
                  'to always enable'),
        )
        group.add_argument(
            '--print-empty',
            action='store_true',
            help='Print empty table if there is no data to show.',
        )

    def add_rows(self, table, column_names, data):
        # Figure out the types of the columns in the
        # first row and set the alignment of the
        # output accordingly.
        data_iter = iter(data)
        try:
            first_row = next(data_iter)
        except StopIteration:
            pass
        else:
            for value, name in zip(first_row, column_names):
                alignment = self.ALIGNMENTS.get(type(value), 'l')
                table.align[name] = alignment
            # Now iterate over the data and add the rows.
            table.add_row(_format_row(first_row))
            for row in data_iter:
                table.add_row(_format_row(row))

    def emit_list(self, column_names, data, stdout, parsed_args):
        x = prettytable.PrettyTable(
            column_names,
            print_empty=parsed_args.print_empty,
        )
        x.padding_width = 1

        # Add rows if data is provided
        if data:
            self.add_rows(x, column_names, data)

        # Choose a reasonable min_width to better handle many columns on a
        # narrow console. The table will overflow the console width in
        # preference to wrapping columns smaller than 8 characters.
        min_width = 8
        self._assign_max_widths(
            stdout, x, int(parsed_args.max_width), min_width,
            parsed_args.fit_width)

        formatted = x.get_string()
        stdout.write(formatted)
        stdout.write('\n')
        return

    def emit_one(self, column_names, data, stdout, parsed_args):
        x = prettytable.PrettyTable(field_names=('Field', 'Value'),
                                    print_empty=False)
        x.padding_width = 1
        # Align all columns left because the values are
        # not all the same type.
        x.align['Field'] = 'l'
        x.align['Value'] = 'l'
        for name, value in zip(column_names, data):
            x.add_row(_format_row((name, value)))

        # Choose a reasonable min_width to better handle a narrow
        # console. The table will overflow the console width in preference
        # to wrapping columns smaller than 16 characters in an attempt to keep
        # the Field column readable.
        min_width = 16
        self._assign_max_widths(
            stdout, x, int(parsed_args.max_width), min_width,
            parsed_args.fit_width)

        formatted = x.get_string()
        stdout.write(formatted)
        stdout.write('\n')
        return

    @staticmethod
    def _field_widths(field_names, first_line):

        # use the first line +----+-------+ to infer column widths
        # accounting for padding and dividers
        widths = [max(0, len(i) - 2) for i in first_line.split('+')[1:-1]]
        return dict(zip(field_names, widths))

    @staticmethod
    def _width_info(term_width, field_count):
        # remove padding and dividers for width available to actual content
        usable_total_width = max(0, term_width - 1 - 3 * field_count)

        # calculate width per column if all columns were equal
        if field_count == 0:
            optimal_width = 0
        else:
            optimal_width = max(0, usable_total_width // field_count)

        return usable_total_width, optimal_width

    @staticmethod
    def _build_shrink_fields(usable_total_width, optimal_width,
                             field_widths, field_names):
        shrink_fields = []
        shrink_remaining = usable_total_width
        for field in field_names:
            w = field_widths[field]
            if w <= optimal_width:
                # leave alone columns which are smaller than the optimal width
                shrink_remaining -= w
            else:
                shrink_fields.append(field)

        return shrink_fields, shrink_remaining

    @staticmethod
    def _assign_max_widths(stdout, x, max_width, min_width=0, fit_width=False):
        if min_width:
            x.min_width = min_width

        if max_width > 0:
            term_width = max_width
        elif not fit_width:
            # Fitting is disabled
            return
        else:
            term_width = utils.terminal_width(stdout)
            if not term_width:
                # not a tty, so do not set any max widths
                return
        field_count = len(x.field_names)

        try:
            first_line = x.get_string().splitlines()[0]
            if len(first_line) <= term_width:
                return
        except IndexError:
            return

        usable_total_width, optimal_width = TableFormatter._width_info(
            term_width, field_count)

        field_widths = TableFormatter._field_widths(x.field_names, first_line)

        shrink_fields, shrink_remaining = TableFormatter._build_shrink_fields(
            usable_total_width, optimal_width, field_widths, x.field_names)

        shrink_to = shrink_remaining // len(shrink_fields)
        # make all shrinkable fields size shrink_to apart from the last one
        for field in shrink_fields[:-1]:
            x.max_width[field] = max(min_width, shrink_to)
            shrink_remaining -= shrink_to

        # give the last shrinkable column shrink_to plus any remaining
        field = shrink_fields[-1]
        x.max_width[field] = max(min_width, shrink_remaining)